Field of the Invention
The present invention relates to a multi-piece solid golf ball of four or more pieces which has a core, an envelope layer, an intermediate layer and a cover (outermost layer). The invention relates in particular to a multi-piece solid golf ball which is competitively advantageous when used by professional golfers and skilled amateurs.
Prior Art
Numerous golf balls have hitherto been developed as golf balls for professional golfers and skilled amateurs. Of these, multi-piece solid golf balls having an optimized hardness relationship among the different layers encasing the core, such as the intermediate layer and the cover (outermost layer), are in widespread use because they achieve both a superior distance performance in the high head-speed range and also good controllability on shots with an iron and on approach shots. Recently, to achieve even better performance such as flight, many four-piece solid golf balls have been described in which an envelope layer is additionally provided between the core and the intermediate layer, thereby giving a ball structure having four layers. Technical literature on such four-piece solid golf balls includes the following published art.
U.S. Published Patent Application No. 2007/0281801 discloses a golf ball in which a urethane material is used as the cover, the hardnesses and thicknesses of the individual layers are adjusted within specific ranges, and the core diameter is made somewhat large. U.S. Published Patent Application No. 2007/0287557 discloses a golf ball in which a highly neutralized resin material is used as the envelope layer material and the ball has been given a structure that is hard on the inside and soft on the outside. U.S. Published Patent Application 2008/0064526 describes a golf ball in which the core hardness profile and the hardnesses of the individual layers have been designed in specific ranges, and a urethane material is used as the cover. U.S. Published Patent Application 2007/0281802 teaches a golf ball in which the core hardness profile is designed in a specific range, a highly neutralized resin material is used as the envelope layer material, and the cover is made relatively soft. U.S. Published Patent Application 2009/0111610 describes a golf ball in which the hardnesses and thicknesses of the individual layers are designed in specific ranges, a highly neutralized resin material is used as the envelope layer material, and a urethane material is used as the cover.
However, with some of these golf balls, although professional golfers and skilled amateurs are able to satisfactorily extend the carry on shots with a driver (W#1), they are unable to achieve a sufficiently high spin performance on approach shots using a wedge. Conversely, there are golf balls which, while capable of maintaining a sufficient spin performance on approach shots, have an insufficient spin rate-lowering effect on shots with a driver (W#1) or an inadequate ability to maintain a straight trajectory on full shots, as a result of which there remains room for improvement in the distance traveled by the ball. Accordingly, there exists a desire for the development of a golf ball which achieves both an excellent distance performance and also an excellent spin performance on approach shots when used in a relatively high head-speed range such as by professional golfers and skilled amateurs.
It is therefore an object of the invention to provide a golf ball which is capable of satisfying at a high level both the flight and control performances desired for use by professional golfers and skilled amateurs.